Weird effect on bolts during baking.

[joeyg1973]

I have never seen this before. I clear powder coat all the heads of the external bolts I clean up on this engine and only this engine... never doing this again. Anyway I went and put the stuff in the oven and it came out somewhat bronze which I figured was because I hadn't watched the cheap toaster oven and it shot the temp too high. So I throw then in some acetone for a while and with wire wheel I get off the powder coat.

Now just to make sure that there is nothing on them I stuff them back in the toaster oven at 450 for 20 minutes. And... they come out completely bronze now. It comes right off with some quick wire wheel work but unless I can solve why these things are doing that I can't really powder coat them.

What is going on with this metal?

[joeyg1973]

Picture of what it should look like.

[SCOTTRODS]

I have never seen this before. I clear powder coat all the heads of the external bolts I clean up on this engine and only this engine... never doing this again. Anyway I went and put the stuff in the oven and it came out somewhat bronze which I figured was because I hadn't watched the cheap toaster oven and it shot the temp too high. So I throw then in some acetone for a while and with wire wheel I get off the powder coat.

Now just to make sure that there is nothing on them I stuff them back in the toaster oven at 450 for 20 minutes. And... they come out completely bronze now. It comes right off with some quick wire wheel work but unless I can solve why these things are doing that I can't really powder coat them.

What is going on with this metal?

There is definitely a process issue. It could be that the radiant heat, straight off the burners, is causing the powder to burn. This also makes sense if you're having an easy time getting the powder removed after cure. Could be the part is changing color too. Heat will discolor metals.... it's just the way it is sometimes.

Shield the parts from the direct radiant heat in whatever you are using, be it a toaster oven or a full sized oven.

Make sure you are not leaving the pieces in for excessive times, and go as close to manufacturer recommendations as possible. If you are going to deviate from that, make sure and use lower temps for a slightly longer soak time.

If the parts are not changing color, the powder is, and likewise if the powder is not the issue, then your parts are getting too hot. Putting the hardware in the oven for a cure session, without coating them first, can test this. At least you can tell if it is the part or the powder that way, and go from there.

[joeyg1973]

It's the part. The second time I put them in the oven was after I got off the coating. I put them in the second time at 450 for only 25 minutes with no powder coating at all and this is the result. I have no clue whats in the metal that could be making this happen. These are steel bolts from the side cover and timing cover of a 1979 Toyota FJ-40 2f motor. I am using Castwell's Super High Gloss Clear. Perhaps I need to bake them at a lower temp for a longer time, but I am not sure how to modify time v. temp as I am powder coating as a hobby right now. Any suggestions on how to make this work would help.

Joe

[SCOTTRODS]

It's the part. The second time I put them in the oven was after I got off the coating. I put them in the second time at 450 for only 25 minutes with no powder coating at all and this is the result. I have no clue whats in the metal that could be making this happen. These are steel bolts from the side cover and timing cover of a 1979 Toyota FJ-40 2f motor. I am using Castwell's Super High Gloss Clear. Perhaps I need to bake them at a lower temp for a longer time, but I am not sure how to modify time v. temp as I am powder coating as a hobby right now. Any suggestions on how to make this work would help.

Joe

I'll shoot you another idea, Joe..... How about some new hardware? If I were putting together something like that, I'd be buying new, unless I was putting color on them anyway. You could always see about having them coated. Better yet, look at the plating stuff on this (caswell) website. These guys have the stuff to make 'em look new again.

[joeyg1973]

I'll shoot you another idea, Joe..... How about some new hardware? If I were putting together something like that, I'd be buying new, unless I was putting color on them anyway. You could always see about having them coated. Better yet, look at the plating stuff on this (caswell) website. These guys have the stuff to make 'em look new again.

Yeah I thought about the new hardware route, but these are JIS bolts with phillips. I can't find replacements like that anywhere. They are unique and that is why I want to use them. The normal metric bolts you get here have all the wrong head sizes as they are not JIS standard. The same bolt length, pitch, and size has a head in JIS of 12MM and 13MM when you get them at your local hardware store. They just won't fit like these do. They are pretty unique. I don't like the look of chrome, but like polished aluminum and steel which is why I haven't gone with the plating method. I did inquire about that from Castwell and they told me that I would need to get their full blown kit and not one of the smaller ones as I would need to get a lot of plating on them otherwise it would just come off after a while in the engine compartment. I actually wanted to go with nickle plating. This is why I am powder coating the heads clear after polishing in a vibratory tumbler so that they hold up the look and don't rust. I did the same thing for the bolts for the oil pan, same JIS with phillips only the bolts were a bit larger and those came out looking GREAT!

[FigureLLC]

steel darkens around 400. 450 definitely does it. i'd say try baking the clear around 350 for an extended cure cycle, but a toaster oven really isn't going to be good for controlling heat. ...even when making toast, in my experience.

[joeyg1973]

steel darkens around 400. 450 definitely does it. i'd say try baking the clear around 350 for an extended cure cycle, but a toaster oven really isn't going to be good for controlling heat. ...even when making toast, in my experience.

Yeap, that's why I have to sit there with my multi-meter with temp probe and watch it like a hawk.

[joeyg1973]

steel darkens around 400. 450 definitely does it. i'd say try baking the clear around 350 for an extended cure cycle, but a toaster oven really isn't going to be good for controlling heat. ...even when making toast, in my experience.

This worked great! Let it sit in the oven at 350 for about 40 minutes.